Rotary rock drilling tool



Nov. 29, 1955 D. B. MACNEIR 2,725,215

ROTARY ROCK DRILLING TOOL Filed May 5, 1953 2 Sheets-Sheet 1 INVENTOR.

00M440 5. nae/nae,

Nov. 29, 1955 D. B. MACNEIR 2,725,215

ROTARY ROCK DRILLING TOOL 2 Sheets-Sheet 2 Filed May 5, 1953 INVENTOR.

2,725,215 ROTARY ROCK-DRILLING TOOL Donald B. Macn'eir, Houston, Tex.

ApplicationMay 5,.1953,-Serial No. 353,134 2' Claims. of. 255-61 invention relates towell drilling tools, and more particularly toan improved drilling tool or drill for use in-cutting through rock formationsv and'the like.

The mainobject of the invention is to provide a novel and improved rotary rock drilling tool which is simple in construction, which provides an efficient cutting and battering action, and which automatically provides a pulverizing action when resistance to rotation of its'central portion: occurs, as when encountering hard rock materials.

A further object of the invention is to provide an improved rota'ry well drilling tool which is relatively inexpensiveto manufacture, which is sturdy in construction, and which greatly speeds up drilling operations, especially through hard rock materials by providing an automatic impact of the tool on the material being cut when said material is" encountered during the course of rotary drilling.

Further Objects and advantages of.- the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure l is a bottom view of a-rotary rock drill constructed in accordance with the present invention,

Figure 2' is a vertical cross sectional view taken on the line 22' of Figure 1.

Figure 3 is a horizontal cross sectional view taken on the line 3-3 of Figure 2.

Figure 4 is a transverse vertical cross sectional view tahenon the line4--4 o-f-Figure 2;

Figure 5' is a horizontal cross" sectional view taken on the line 5-5 of- Figure 4:

Figure 6 is a perspective view of the inner bit member of the rotary cutting drill of Figures 1 to 5.

Referring to the drawings, the illustrated rbcli drilling tool is designated generally at 11 and comprises a main cylindrical body 12 adapted to be rotated by. a suitable mechanism formingno part of the present invention.

internal threads 13, and threadedly engaged thereon is the externally threaded top end 14 of a tubular upper drill section 15 formed in its upper part with a downwardly tapering axial bore 16 and with a cylindrical counterbore 17 in its lower part having internal threads 18 at its bottom end. Threadedly engaged with the threads 18 is a reduced upper portion 19 of a lower bit section 20 formed with a central bore 21, said central bore having the downwardly tapering intermediate portion 22 and a cylindrical, reduced lower end portion 23. The lower bit section 20 is formed with the annular recess 24, and in the annular recess 24 are the generally conical rotary cutters 25, journaled on respective generally radially arranged shafts 26 mounted in the lower end portion of the bit section 20. As shown in Figure 2, the shafts 26 are preferably inclined upwardly and outwardly relative to the central portion of the bit section 20 and are provided with reduced inner end portions 27 which are received in suitable bores formed in the central portion 28 of the bit section 20. The outer 2,725,215 Patented Nov. 29, 1955 ice bores formed in the outer portion of the bit section 20,-

as shown in Figure 2. The conical rotary cutter elements 25 are freely mounted for rotation in the annular recess 24, and said rotary cutters are provided with suitable cutting teeth 29 which are exposed at the lower end of the bit section 20. The cutting teeth 29 provide a grinfd ing and cutting action on material subjacent to the bit section 20, whereby said material iscrushed and substantially pulverized responsive to the rotation-of thema-in body 12.,

In accordance with the conventionalpractice, suitable means is provided for carrying away the crushed rock fragments, as for example,- mud may be pumped downwardly through the mainbody 12' andth-rough the bore 21 into the annular cavity 24 throughrespective passages 30, as shown in Figure 2, the mud" serving to flush the crushed material outwardly frombeneath the tool; The mud and crushed material is pumped upwardly externally of the main body 12 in the usualmanner, thus removing the debris resulting from the cutting action of the tool.

The lower bit section 20 is provided inwardly of the rotary cutting elements 25 with the cutting teeth-31 which cooperate with-the rotary cutting elements 25' to crumble the material subjacent the central portion of the tool responsive to the rotation of the tool in. the bore hole. Designated at'32'is a pilot bit'of the star drill type-having the bottom radial cutting edges'33; Thepilotbit 32 is formed at its top end with the-enlarged head 34 which isrotatably received in-the recess 17,- the head- 34 being formed with the smoothly inclined cam elements 35, 35 which terminate in the substantially vertical endshoulders 36, 36 shown in- Figure 6. The annular topwall of the cylindrical recess 17 is formed with similar smoothly inclined cam surfaces 37 having vertical terminating shoulders 38, the elements 37 and 38 being directed in opposition to the elements- 35 and 36- carried on the enlarged head 34 of the star drill member 32;

The pilotbit 32" is formed with passages 39' through which the wash liquid flows downwardly from bore'2'1': This delivers a' plurality of jets arranged inacircular pattern around the star drill point which clears the bottom of the drilled hole and also serves to cool the star drill.

The cylindrical recess17 is-of sufiicient height to allow the head member 34 to movevertically therein througha distance slightly greater than the combined-heights of'the shoulders 36' and 38. Normally,inamely, when the inclined cam surfaces 35 and 37 engage each other, the cutting edges 33 of the pilot bit 32 are located slightly below the'rotary cutting elements 25, whereby the lower end of the bit 32 projects slightly below the remainder of the cutting edges of the tool. Thus, when the tool is rotating through relatively soft material, the pilot bit 32 rotates along with the remainder of the tool, the torque of the main portion of the tool being transmitted through the cam surfaces 37 and 35 to the pilot bit 32, since rotation of the pilot bit 32 is relatively unopposed. However, when relatively hard material is encountered, the cutting teeth 33 of the pilot bit engage said material, whereby resistance to rotation of the pilot bit 32 is developed, causing the cam surfaces 37 on the top wall of the cylindrical recess 17 to ride upwardly on the inclined top cam surfaces 35 of the head 34 of pilot bit 32. As the cam surfaces 37 are carried past the ends of the cam surfaces 35, the main portion of the tool is allowed to descend abruptly as the depending cam elements on the annular top wall of recess 17 move past the shoulders 36. This delivers a heavy impact to the head 34 of the pilot bit 32 and the rotary cutters 25, causing the pilot bit to crush the hard material in which it is engaged and causing the material adjacent to the pilot bit 32 to be also crushed by the downward movement of the cutting edges 31 and rotary cutters 25 as the main body of the tool drops. This action occurs continuously as the main body 12 of the tool is rotated, and, with the cooperation of the rotary cutting members 25, the bore hole is rapidly formed through the hard rock material. As above explained, when the drill encounters relatively soft material, the pilot bit 32 rotates along with the remainder of the tool and the above described hammering action does not occur. However, when hard material is encountered, the hammering action is automatically obtained by the cooperation of the cam elements on the head 34 and on the top wall of the cylindrical recess 17, as above described.

Obviously, difierent forms of pilot bits could be employed in place of the bit 32, since a similar action will be obtained regardless of the particular shape of their cutting edges. The automatic hammering action will be obtained due to the fact that the pilot bit is held stationary while the remainder of the drill rotates to cause the cam elements 37 to move past the shoulders 36, whereby the Prior to the engagement of the pilot bit 32 in the hard rock formation, the cam formations 37 deliver the necessary force required to seat the cutting edges 33 of the bit 32 in the hard rock formation until the bit is rigidly held, whereupon the cam elements 37 climb along the cam surfaces 35 of the rigidly held pilot bit 32.

As is clearly shown in Figures 2 and 4, the head 34 of the pilotbit 32 is formed with the passages 39 through which the circulating mud passes from the bore 16 into the bore 21, subsequently flowing through the passages 30 into the annular recess 24 and thence outwardly past the rotary cutters 25, as above described, to remove the debris resulting from the operation of the bit in the usual manner.

While a specific embodiment of an improved rotary rock drilling tool has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. In a rotary drilling tool, a drill body comprising a tubular upper bit section adapted to be connected to the lower end of a drill pipe, said upper section having a bore through its upper part and a counterbore through its lower part and communicating with said bore, said counterbore being larger in diameter than said bore and therewith defining a shoulder at the upper end of the counterbore, a tubular lower bit section having a reduced threaded upper end portion threaded into said counter bore, said threaded upper end portionbeing spaced below said shoulder, said lower bit section having an axial bore therethrough communicating with said counterbore, said axial bore being smaller in diameter than said counterbore, and a pilot bit comprising a pilot bit shank slidably and rotatably engaged through said axial bore and extending in said counterbore, said shank having an upper end, an enlarged head on the upper end of the shank slidably and rotatably engaging said counterbore between said shoulder and said reduced threaded upper end of the lower bit section, said head being shorter than the distance between said shoulder and said reduced threaded upper end of the lower bit section, opposed cam surfaces on said shoulder and on said head, and passages extending through said head and communicating with said counterbore and with the bore of the upper bit section.

2. In a rotary drilling tool, a drill body comprising a tubular upper bit section adapted to be connected to the lower end of a drill pipe, said upper section having a bore through its upper part and a counterbore through its lower part and communicating with said bore, said counterbore being larger in diameter than said bore and therewith defining a shoulder at the upper end of the counterbore, a tubular lower bit section having a reduced threaded upper end portion threaded into said counterbore, said threaded upper end portion being spaced below said shoulder, said lower bit section having an axial bore therethrough communicating with said counterbore, said axial bore being smaller in diameter than said counterbore, and a pilot bit comprising a pilot bit shank slidably and rotatably engaged through said axial bore and extending in said counterbore, said shank having an upper end, an enlarged head on the upper end of the shank slidably and rotatably engaging said counterbore between said shoulder and said reduced threaded upper end of the lower bit section, said head being shorter than the distance between said shoulder and said reduced threaded upper end of the lower bit section, opposed cam surfaces on said shoulder and on said head, and passages extending through said head and communicating with said counterbore and with the bore of the upper bit section, said axial bore of the lower bit section having an enlarged upper portion spacedly surrounding the pilot bit shank, said lower bit section having a lower end having an annular recess therein, cutting means in said recess, and ducts leading into said recess from said enlarged upper portion of the axial bore of the lower bit section.

Woodruft et al. Feb. 11, 1930 Stokes Feb. 6, 1951 

